Apparatus for cooling gaseous media



3 Sheets-Sheet l .1. HANNY APPARATUS FOR COOLING GASEOUS MEDIA Jan. 14,1964 Filed Nov. 16, 1961 FIG. 1

Q L L E Ev TE; T J r fpa r A u QM m INVEFATOR JOST HANNY BY l' wlwsfpbu' ATTORNEYS I TH Jan. 14, 1964 J. HANNY 3,117,423

APPARATUS FOR COOLING GASEOUS MEDIA Filed Nov. 16, 1961 3 h s-Sh 2INVEIETOR JOST HANNY ATTORNEYS Jan. 14, 1964 J. HANNY APPARATUS FORCOOLING GASEOUS MEDIA 3 Sheets-Sheet 3 NVE I TQR JOST HANNY ATTORNEYSA044, M W MJW Filed NOV. 16, 1961 United States Patent Ofifice idiiAZPatented Jan. 14, 19 34 AFAPATUS FSR CQQLENG GASEQUS MEDKA Jest Hanny,Winterthur, witzerland, assignor to ulzer Freres, Societe Anonyme,Winterthur, Switzerland, :1

Swiss company Fiied Nov. 16, 1%1, Ser. No. 152,694 Claims priority,application Switzerland Aug. 15, 1961 9 Claims. (iii. 62-402) Thisinvention pertains to a system for cooling gaseous media, in whichsystem an expansion turbine which operates at low temperature and inwhich the gases are expanded with the performance of work, is coupled bymeans of a shaft supported in gaseous hearings to a turbo compressorwhich operates at a higher temperature. The invention relates moreparticularly to such an arrangement in which the gas, which performs abraking function in the turbo compressor, flows in a closed cycleseparate from the cycle of the working substance in the turbine, thecompressor gas being recirculated through a heat exchanger and throughan adjustable throttling device, and in which moreover gas of the samecomposition is used in the turbine, in the compressor, and in thegaseous bearings.

Apparatus according to the invention, or plural sets of such apparatus,may be employed in the gas cycle of a rectifier, liquefier, or lowtemperature refrigerating plant employing air or other suitable gas.Such plural installations may be operated either in series or inparallel.

Upon the occurrence of pressure variations or pressure drops at theturbine, gas at relatively high temperature will flow out of the brakingcompressor through the gas bearings, which are also fed with hightemperature gas, and thence into the turbine. This results insubstantial heat losses into the refrigeration cycle. For theirdissipation substantial energy must be expended. The heat streaming intothe cold portion of the system and the volume of gas which carries itare, other things being equal, dependent upon the volume of the brakingcompressor system. It is therefore desirable to reduce this volume sofar as possible.

On the other hand, the heat exchanger in the braking device, whichserves for the abstraction of energy transmitted from the turbine to thecompressor, must deliver a specified amount of heat to the coolingmedium, which is usually water. It is therefore desired to promote heattransfer Within the braking part of the system, particularly in the heatexchanger. It is only in this way i.e. by improved heat transfer throughthe exchange surfaces, that with a given amount of heat to be disposedof and with a given temperature difference between the medium to becooled and the cooling medium, these surfaces can be held small andthereby, other things again being equal, the volume of the brakinginstallation be held down. Improved heat transfer can, as is known, heachieved by raising the streaming velocity of the gas in the brakinginstallation, thereby reducing the streaming cross section.

Let the thermal diameter a' be defined for the entire brakinginstallation as the quotient of the four-fold volume of the gas cycle ofthe braking installation divided by the total surface through which heatexchange is to take place. If in addition to an increased streamingvelocity the thermal diameter d of the entire braking installation ismade as small as possible, the result is a further improvement in heattransfer. In this fashion, for a given quantity of heat and a specifiedtemperature drop, the surface necessary for heat exchange can be heldsmaller than that required with a higher streaming velocity and biggerthermal diameter d This means however that the volume of the completebraking cycle will be very small, first because of the increasedpressure drop and the consequent increase in streaming velocity, andalso in view of the small exchange surface required by the thus furtherincreased heat transfer and lastly because of the decline with d of theratio of volume to surface.

According to the invention, and in contrast to prior installations inwhich pressure drop has been so far as possible avoided in the heatexchanger, the pressure drop corresponding to the substantial part ofthe pressure change produced by the compressor occurs in the heatexchanger. The invention is therefore characterized by the fact that thebraking part of the system is so constructed that-to the extentpermitted by the regulating capacity of the throttling deviceof thepressure change produced in the compressor, at least as large a fractionis dissipated in the heat exchanger as in the throttling device.

In this connection it is to be noted that with various gases such ashelium or hydrogen, throttling at high temperatures produces a riserather than a fall in the gas temperature.

Preferably the heat exchanger may be provided in the raking part of thesystem in the form of a number of narrow, long streaming conduits ofsplit-tube or ribcooler type. The term split-tube cooler is used todenote a cooler in which the medium passes in opposite directionsthrough coaxial tubes. With such an installation it is desirable thatthe thermal diameter of the entire braking installation as above definedshall not exceed 10 A further embodiment of the invention ischaracterized by the fact that the braking part of the system isconstructed as a self-contained closed unit in which the heat exchangeris built directly onto the compressor, the throttling device beingaxially movable and being arranged coaxially with the compressor andsurrounded by the heat exchanger.

By means of the system of the invention the gas streaming in the brakingapparatus is circulated at a high velocity in a closed path. Thiseffects good heat transfer. In consequence there is required arelatively small transfer surface for abstraction of the energydeveloped in the turbine. In consequence the physical size of thebraking device can be held small by comparison with similar systems ofthe prior art.

Further features of the invention will appear from the followingdescription of two embodiments, to be taken in conjunction with theaccompanying drawings in which:

FIG. 1 shows an axial section on the line 11 of FIG. 2 through a brakingdevice according to the invention, together with the coupling thereof toan expansion turbine which is disposed in the cyclical path of thecoolant in a refrigeration plant;

FIG. 2 is a section on the line 22 of FIG. 1;

FIG. 3 shows a modified embodiment of the invention on the sameconvention as that of FIG. 1; and

FIG. 4 shows a section on the line 44 of FIG. 3, at an enlarged scale.

Like reference characters identify corresponding elements of structurein the various figures.

Referring to FIG. 1, the cold gas flows through the input line 1 intothe high pressure space 2 of the turbine 3 and leaves the turbine, afterexpansion, through a funnel-shaped difiuser 5 and conduit 4, thediifuser being fixed to the housing 6 of the turbine. The outlet channelof the turbine is formed by means of a guide piece 8 which is similarlyfastened to the housing 6 and which leads to diffuser 5. The housing 6in turn is fastened to an insulating plate 20 of the low temperaturerefrigerating apparatus (not shown), which is disposed in a vacuum.

The turbine 3 is coupled to the rotor Iii of the turbo compressor bymeans of the shaft 9. The low pressure inlet and high pressure outletconduits 11 and 12 of the compressor are disposed in a compressorhousing 13 fastened to the housing 6 of the turbine. An inner portion13a of the housing 13 is fixed by welding to a cylinder 47. Theseparation between the cold and warm parts of the apparatus is indicatedat the dot-and-dash line A, the cold portion being above this line. Theshaft 9, which may be disposed either horizontally or verticallyaccording to the makeup of the installation, is borne in a gas bearingincluding segments 14. This bearing is disposed in a hollow space 15 ofthe turbine housing 6. The space 15 is divided into two parts by meansof an enveloping element 17, to define an inner space 18 which housesthe segments 14 and the fixed parts 19' of the bearing. Gas fornourishment of the bearing is fed from a separate source such as abottle (not shown) through a conduit 21 in the compressor housing 13into the spam 18. From the space 18 it passes through distributionchannels 22 and a pressure equalizing space 23 to the segments 14. Afterpassing through the bearing, the gas flows via an annular space 24 andthe conduit 25, and also through openings 26 in the part 27, into thespace 15. From the space 15 it is led out of the apparatus through aconduit not shown.

Packings necessary to be provided between the various spaces and againstthe atmospheric exterior are indicated at 28.

The braking part of the apparatus is formed by the compressor 10 withits low pressure side 11 and its high pressure annular space 12, theseelements being disposed in the compressor housing 13. It also comprisesthe heat exchanger 31 connected directly to the housing 13, and athrottling device 32. The gas compressed in the compressor 1% passesfrom the space 12 as indicated in FIGS. 1 and 3 by means of the arrowsdirectly into the channels 33 of the cylindrical heat exchanger 31, allwithin the closed path of the braking medium. After cooling in the heatexchanger 31, the gas penetrates to an annular space 34 which is coupledto the low pressure side 11 of the compressor via a connection 35 whichis adjustable by means of the throttling device 32. This device isdisposed coaxially with the compressor 19 and may be adjusted by meansof a hand wheel 36 operating on an adjusting device. On the other hand,it is possible to control the setting of the throttling device 32automatically, for example as a function of the temperature in thecooling circuit. The device 32 has the function of making possibleadjustment of the rotational speed or the turbine within specifiedlimits. To this end it is made axially movable by means of a spindle 33which moves in a central bore 39 of the exchanger 31. The device 32 istherefore disposed in an envelope 4%, likewise positioned within thebore 39.

From the annular space 12 of the compressor the gas in the braking cyclepasses in the embodiment of FIGS. 1 and 2 into axially extending laminarchannels 33 of the heat exchanger 31, having a semi-circular crosssection in planes perpendicular to the system axis. The gas passesthrough these channels in parallel. These channels possess between theirradially inner and outer side walls rib-shaped heat transfer sheetshaving the shape of narrow strips 42 similar in construction toplate-fin coolers. These strips have a short extension axially of thesystem, and axially successive strips may be staggered with respect toeach other circumferentially of the system axis 1. From the channels 33the gas penetrates into the lower annular space 43 and from the latterinto similar conduits 33:: which are similarly traversed in parallel,but in the opposite axial direction (upward, in FIG. 2). From these thegas passes into the space 34 and thence through the device 32 into theinlet space 11 of the compressor 16. The channels 33 and 33a areseparated by means of the cylinder 47.

Between the channels 33 and 33a there are disposed semi-circularintermediate laminar spaces 48 which are filled with cooling water. Thiswater is led into the heat exchanger 31 through a connection 49, intothe circular segment-shaped space 49a. This space is stepped as requiredby the varying length of the channels 33 imposed on them by the shape ofthe inner portion 13a of the compressor housing. It extends radiallyinward however, even though at reduced cross section, to the vicinity ofthe throttlng device 32. The water thus passes into the heat exchanger,traversing the intermediate spaces 48 circumferentially of the axis inparallel flow as indicated in FIG. 2 before it emerges from theexchanger 31 via the oppositely disposed segment-shaped space 56a andthe connection 50, positioned diametrically opposite the conduit 49 atthe lower end of the exchanger 31. In order to permit passagetherethrough of the cooling water, the cylinder 47 is provided withopenings (not shown) in the vicinity of the segment spaces 49:: and 5%which extend over the length of the conduits 33. The cooling medium andthe gas to be cooled accordingly flow transversely of each other in theembodiment of FIGS. 1 and 2.

The embodiment of FIGS. 3 and 4 diifers from that of FIGS. 1 and 2simply in the construction of the heat ex changer 31. In FIGS. 3 and 4this exchanger takes the shape of a split-tube cooler. The compressorhousing 13 and the exchanger 31 are here also made up of several parts.Consequently the boundaries of the annular space 12 are defined in partby an intermediate element 16 which encloses the compressor intake 11and which includes bores 51 for exit of the gas from the annular space12. In this embodiment the gas, after leaving the annular space 12,passes successively through the inner and outer coaxial spaces definedby the tubes 61 disposed concentrically in bores 63' of the heatexchanger block. In this flow, the gas passes from one pair of coaxialspaces to a serially succeedin pair via the intermediate spaces 62 and63. The annular junction space 62 is disposed in a further element 54which houses the ends of the tubes 61. The element 54 is disposedbetween the intermediate piece 16 and the block 31 of the heatexchanger. In the heat exchanger the annular space 63 is separated fromthe space 34 by means of an annular insert 55.

The flow path for the cooling water is formed in a manner similar tothat of the gas. The water passes through the bore 72 and the annularspace 63 into the tubes 64 which lead to the bores 65 of the exchanger31 coaxial therewith. Series-connected coaxial pairs each including thecoaxial passages 54 and 65 are connected together via annular spaces 69in the base plate 67 and annular spaces 70 in the heat exchanger block.The ends of the tubes 64 are fixed in an element 71 disposed between theheat exchanger block and the base 67. The cooling water leaves theinstallation at the opening 66 in the base.

Viewed in cross section of the heat exchanger block, the bores 60' forthe gas and 55 for the cooling medium are disposed in an alternatingdisplaced relation to each other on the periphery of circles or" unlikeradius. The heat exchanger is therefore of the counter flow type.

The invention is not limited to the details of the structure shown. Thethrottling device can be disposed at other positions within the circularflow path, for example either downstream of the diffuser 12a or in thebore 51 of the element 16.

By means of the construction of the braking element which has beendescribed, and in which a substantial part of the pressure rise producedin the compressor is dissipated in the heat exchanger itself, the gas iscaused to flow in a closed path at high velocity. By this means the heattransfer from the gas to the heat exchange surfaces is substantiallyincreased. The good heat exchange thus achieved can be further improvedif the thermal diamter d of the braking structure is held small. With agiven heat exchange surface a diminution in d corresponds, by definiton,to a reduction in volume. Moreover as a result of the reduction in dthere occurs an increase in the coefiicient of heat transfer which,other things being equal, makes possible further reduction in the sizeof the heat exchange surface which indeed is conditioned by the quantityof heat to be abstracted, by the heat transfer coefficient between thegas and the heat transfer surface, and by the temperature differencebetween them. In consequence there must occur a further decline in thevolume necessary for the braking part. By means of the inventiontherefore it is possible to make the volume of the braking part small toa high order without encountering difficulties in dissipation of theenergy liberated by the turbine. As initially indicated, this re ductionin the volume of the braking part substantially decreases the heatlosses in the turbine incident upon variations in pressure.

I claim:

1. Apparatus for cooling at gas comprising an expansion turbine throughwhich said gas is expanded, said turbine having a shaft supported in agaseous bearing, a turbo compressor coupled to said shaft, meansdefining for said compressor a closed path within which a gas iscirculated by said compressor, a heat exchanger and an adjustablethrottling device disposed in series in said path, said compressor andclosed path being so proportioned that at least as much of the pressuredifference between the inlet and outlet of said compressor is dissipatedin said heat exchanger as in said throttling device.

2. Apparatus for cooling a gas comprising an expansion turbine throughwhich said gas is expanded, said turbine having a shaft supported in agaseous bearing, a turbo compressor coupled to said shaft, meansdefining for said compressor a closed path within which a gas iscirculated by said compressor, the gas in said turbine, compressor andbearing being of substantially the same composition, a heat exchangerand an adjustable throttling device disposed in series in said path,said compressor and closed path being so proportioned that at least asmuch of the pressure difference between the inlet and 3 outlet of saidcompressor is dissipated in said heat exchanger as in said throttlingdevice.

3. Apparatus according to claim 1 in which the ratio of four times thevolume of said path expressed in cubic centimeters to the area of theheat exchange surface in said heat exchanger, expressed in squarecentimeters, does not exceed 1.0 cm.

4. Apparatus according to claim 2 in which the heat exchanger comprisesa plurality of long, narrow, streaming channels through which flows thegas from the compressor.

5. Apparatus according to claim 1 wherein the heat exchanger takes theform of a ribbed cooler.

6. Apparatus according to claim 1 wherein the heat exchanger comprises aplurality of annular spaces coaxial in a common axis, means connectingradially alternate of said spaces in series for flow therethrough of gasfrom said compressor, and means to pass a cooling medium through theothers of said spaces.

7. Apparatus according to claim 1 wherein the heat exchanger takes theform of a split tube cooler.

8. Apparatus according to claim 1 wherein the heat exchanger comprises aplurality of cylindrical arrays of blind bores in a heat exchange block,said arrays being coaxial in a common axis, a tube disposed in each ofsaid bores, means to circulate gas from said compressor through thetubes and bores of radially alternate of said arrays in series, andmeans to circulate a cooling medium through the tubes and bores of theothers of said arrays in series.

9. Apparatus according to claim 4 wherein the turbo compressor and heatexchanger constitute a self-contained unit with the heat exchangerarranged coaxially of the compressor and with the throttling devicedisposed within the heat exchanger.

References Cited in the tile of this patent UNITED STATES PATENTS2,740,267 Bayard Apr. 3, 1956 FOREIGN FATENTS 870,091 Great Britain June14, 1961

1. APPARATUS FOR COOLING A GAS COMPRISING AN EXPANSION TURBINE THROUGHWHICH SAID GAS IS EXPANDED, SAID TURBINE HAVING A SHAFT SUPPORTED IN AGASEIOUS BEARING, A TURBO COMPRESSOR COUPLED TO SAID SHAFT, MEANSDEFINING FOR SAID COMPRESSOR A CLOSED PATH WITHIN WHICH A GAS ISCIRCULATED BY SAID COMPRESSOR, A HEAT EXCHANGER AND AN AD-